Systems And Methods For Electroplating Embossed Features On Substrates

ABSTRACT

Systems and methods for electroplating embossed features on substrates are disclosed. In an exemplary implementation, a method may include positioning a device in close proximity to an anode. The device may have embossed trenches. The method may also include delivering pressurized electrolyte to the anode. The method may also include activating electrical power between the anode and the device. The metal ions migrate into the embossed trenches to form electroplated metal traces on the device

BACKGROUND

Electroplating is a well-known technique for covering surfaces of a substrate with a metal. In general, electroplating systems include a tank for holding a chemical solution or “plating bath” which contains the metal to be plated, an anode (positive charge), and a cathode (negative charge). A substrate to be electroplated is placed in the plating bath and a charge is applied, causing the metal to come out of solution and deposit on the substrate.

Electroplating techniques arc used for a wide variety of applications, such as, in computers, mobile phones, and other electronic devices, to name only a few examples. Advanced techniques may be used to fabricate more elaborate devices. For example, to fabricate electrical circuits that drive a pixilated flexible display (or other flex circuits), a conductive substrate is first coated with a resin, patterned with traces by pressure-embossing, and then cured. The substrate is then placed into the plating bath so that the resin removed by the embossing is replaced with electroplated nickel (or other metal).

It is often difficult, however, to maintain a uniform plating thickness along the traces on the substrate during the electroplating process because of radical asymmetry and/or variation in trace density inherent in more complicated circuit designs. Plating “shields” are physical, non-conductive obstructions that may be placed between the anode and cathode in the plating tank to affect more uniform plating thickness through current density redirection. Although reasonably effective, shields must be modeled, designed, and fabricated specifically for each substrate that is to be electroplated. Segmented anodes also may be used to help bias the current flow away from edges and toward areas of greater trace concentration, but with a similarly marginal effect. In general, these techniques rely on trial and error and are application specific.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 a-b show a side, cross-sectional view of an exemplary planar electroplating system which may be implemented for electroplating embossed features on a substrate, wherein (a) shows a partially-plated metal trace, and (b) shows a completely-plated metal trace.

FIG. 2 shows a side, cross-sectional view of an exemplary roll-to-roll electroplating system which may be implemented for electroplating embossed features on a substrate.

FIG. 3 is a flowchart illustrating exemplary operations which may be implemented for electroplating embossed features on a substrate.

DETAILED DESCRIPTION

Exemplary systems and methods described herein for electroplating embossed features on a substrate may be used to improve: plating thickness uniformity and enables greater flexibility in device design. The electroplating systems and methods use a conductive web substrate as the cathode, and replace the part-specific anode and shield combinations of conventional electroplating systems with a single, close-proximity anode that serves as both a current source and an electrolyte supply vessel. The anode “smooths out” both the current density and the metal ion flow to the device, and thus results in a more uniform metal buildup during the deposition process. The close-coupled anode configuration also enables the large volume, open plating bath to be reduced in size or even eliminated altogether. The conductive web substrate results in traces only where the web is exposed to the electrolyte (the bottom of the trenches), and nowhere else.

Exemplary System

FIGS. 1 a-b show a side, cross-sectional view of an exemplary planar electroplating system 100 which may be implemented for electroplating embossed features on a substrate 110. FIG. 1 a shows a partially-plated metal trace 112 on the substrate 110 (e.g., during the electroplating procedure). FIG. 1 b shows a completely-plated metal trace 114 on the substrate 110 (e.g., following the electroplating procedure).

In an exemplary embodiment, the substrate 110 may be prepared in advance for the electroplating procedure by coating the substrate with a dielectric resin 115 that protects the surface of the substrate 110 from being plated during the electroplating procedure. The resin may then be pressure-embossed to remove a portion of the resin and create “trenches” 117 a-b exposing conductive portions 118 a-b of the substrate 110 corresponding to the desired traces that are to be electroplated. After curing, the substrate is ready for the electroplating process, e.g., using system 100.

Exemplary system 100 may comprise a plating fixture 120. The plating fixture 120 may be manufactured of a non-conductive material (e.g., plastic), and holds a small fluid plenum 122 of heated electrolyte 124. The electrolyte 124 may be provided to the plating fixture 120 by an electrolyte supply system 130. The supply system 130 may include an electrolyte reservoir 131, a pump 132, a valve 133, a heater 134, and a filter 135. During operation, the supply system 130 provides a metered, pressurized supply of warm, particle-free electrolyte to the plating fixture 120.

It is noted that the components shown in FIG. 1 a are intended only to illustrate one example of a system 100 which may be implemented. Other embodiments are also contemplated and may include additional components, components comprised of multiple parts, and/or fewer components. The system 100 is not limited to those components shown.

The plating fixture 120 is designed to support an anode device 140. In an exemplary embodiment, the anode device 140 is a composite anode. As better shown in the cut-away 145 in FIG. 1 a, the anode 140 may comprise a thick metal-doped porous ceramic layer 141, sandwiched between two similar but thinner, non-conductive layers 142 a-b.

The conductive porous ceramic material 141 has been used for some time in fuel cells, for the creation of hydrogen peroxide, and in metals production. Low flow-resistance to liquid, however, is a less-common attribute and requires a particularly suited material. By way of example, such a material is described, e.g., in U.S. Pat. No. 4,892,857 titled “Electrically Conductive Ceramic Substrate” of Tennent, et al. and assigned to Corning Incorporated (Corning, N.Y.). These and other materials now known or later developed may be used to implement the described systems and methods.

It is noted that the anode 140 may be a “sacrificial” anode, wherein the anode itself provides at least some of the metal ions for the electroplating process and is disposed of when there are insufficient metal ions remaining in the anode for the electroplating process. Alternatively, the anode 140 may be a “non-sacrificial” anode, wherein the metal ions are provided primarily by the heated electrolyte 124. In any event, use of a porous conductive ceramic as the anode enables the substrate 110 that is to be plated to be positioned against (or very close to) the anode 140 during the electroplating process.

The system 100 may also comprise an electric power supply 150. In an exemplary embodiment, the electric power supply 150 may be a regulated DC power supply selected to provide the electrical current necessary for the electroplating process. In any event, the electric power supply 150 electrically connects the anode 140 to the substrate 110 (which serves as the cathode in the electroplating circuit).

During operation, a device (e.g., the resin-coated and embossed substrate described above) is placed over the anode 140 in the plating fixture 120. The pump 132 is activated, providing a metered flow of heated electrolyte 124 to the small plenum 122 under the anode 140 in the plating fixture 120. As the fluid level rises within the plating fixture 120, air is forced out through the porous anode 140. The electrolyte 124 reaches the anode 140, and by virtue of its being hydrophilic, the anode 140 becomes fully wetted. The electrolyte 124 then wets the surface of the device. Flowing electrolyte 124 may be collected and returned to the main supply reservoir 131.

In some embodiments, a slight uniform pressure may be applied to the device to limit the fluid-filled gap between the device and anode 140 so that it is only a very thin film. The power supply 150 is then activated and the metal ions from the electrolyte 124 (e.g., when using a non-sacrificial anode 140) and/or from the doped internal layer of the anode (e.g., when using a sacrificial anode 140) migrate to the exposed surfaces 118 a-b of the substrate 110 (e.g., in trenches 117 a-b as illustrated by arrows 160). If the plating inadvertently makes contact with the anode 140, the anode's outer layer 142 a-b of non-conductive ceramic prevents short-circuiting of the electroplating circuit.

The exposed conductive surfaces 117 a-b on the device correspond to the embossed trenches 118 a-b (e.g., the desired traces). Accordingly, the metal ions accumulate as electroformed features only in these trenches 118 a-b. When the desired plating thickness is achieved (e.g., when the metal has accumulated so that it is flush with the surrounding resin as shown in FIG. 1 b), the electrical power 150 may be disconnected (as indicated by the “X” in FIG. 1 b) and the device removed for rinsing and drying.

The system 100 enables improved plating thickness uniformity. Proper electrical performance of the device depends on predictable trace resistance, which can only be achieved through predictable trace thickness. Embodiments described herein reduce or altogether eliminate the uncertainty inherent in conventional processes. The system 100 is also universally applicable. Predictable trace thickness may be achieved without regard to device design. The system 100 also reduces the size and complexity of the electroplating system. There is no need for a large open tank (less real estate, less environmental impact), no need for a large volume of plating solution (lower cost), and fewer accessories are needed (no shields or mixer is required). The system 100 also enables better temperature control. The temperature uniformity of the much-reduced, essentially enclosed volume of electrolyte is easier to maintain at a constant level.

It is noted that the system 100 described above is shown for purposes of illustration only, and is not intended to be limiting. Other embodiments are also contemplated. For example, the electroplating system described above may also be effectively adapted to a high-throughput manufacturing environment, as described below with reference to FIG. 2.

Previous roll-to-roll electroplating systems included a series of tanks through which the substrate is drawn. The anodes and shields within these tanks had to be sized and located somewhat generically to roughly achieve their intended purposes. However, the anodes and shields could not move with the substrate and therefore could not effectively accommodate the subtleties of multiple device designs.

FIG. 2 shows a side, cross-sectional view of an exemplary roll-to-roll electroplating system 200 which may be implemented for electroplating embossed features on a substrate 210 in a high-throughput environment. It is noted that 200-series reference numbers are used to refer to similar components already described above with reference to FIGS. 1 a-b, and therefore may not be described again with reference to FIG. 2.

In the exemplary embodiment of system 200 shown in FIG. 2, the anode 240 may be configured as a rotating electrolyte-filled “drum” or cylinder 270 to enable continuous roll-to-roll plating. A supply system 230 may be implemented to deliver electrolyte 224 into the drum 270 via piping 280. In one embodiment, system 200 includes an electrolyte recovery system 285 to recycle the electrolyte.

During operation, the supply system 230 pressurizes the electrolyte 224 in drum 270, pushing the electrolyte 224 out from inside the drum 270 and into close proximity of the substrate 210. The process is continuous as the substrate is wrapped around at least a portion of drum 270. That is, the new substrate 210 with exposed metal portions 217 enters on one side of the drum (as shown in inset 290), contacts the drum 270 during the electroplating process, and is removed after the electrolyte has been deposited on exposed metal portions 217 (as shown in inset 291). It is noted that there is no relative motion between the anode and the device during the electroplating process, e.g., as indicated by contact points 275 a-g.

Exemplary Operations

FIG. 3 is a flowchart illustrating exemplary operations which may be implemented for electroplating embossed features on a substrate. Operations 300 may be implemented by the system described above, e.g., by an electronic controller executing logic instructions on one or more computer-readable medium. When executed by the controller, the logic instructions may program the system as a special-purpose machine that implements the described operations. However, the operations are not limited to automatic implementation, and may also be implemented manually, or in a combination of manual and automatic process steps. In an exemplary implementation, the components and connections depicted in the figures may be used.

In operation 310, a device having embossed trenches may be positioned over an anode. For example, the device may be positioned in a planar production configuration (e.g., as shown in FIGS. 1 a-b). Or for example, the device may be positioned in a roll-to-roll production configuration (e.g., as shown in FIG. 2).

In operation 320, a metered flow of heated electrolyte may be delivered under the anode. As the level of the heated electrolyte rises within the fixture, air is forced out through the porous anode. The heated electrolyte eventually reaches the anode, which becomes fully wetted. The heated electrolyte then wets the surface of the device. In some embodiments, excess heated electrolyte may be collected and returned to the main supply reservoir. Also in some embodiments, a slight uniform pressure may be applied to the device to limit the fluid-filled gap between the device and the anode.

In operation 330, electrical power may be activated between the anode and the device. When power is applied in operation 330, metal ions migrate into the embossed trenches to form electroplated metal traces on the device. In an exemplary embodiment, metal ions may migrate from the electrolyte (e.g., where a non-sacrificial anode is used). In another exemplary embodiment, metal ions may migrate from a doped internal layer of the anode (where a sacrificial anode is used). In yet another exemplary embodiment, metal ions may migrate from both the electrolyte and a doped internal layer of the anode.

Once the desired plating thickness has been reached (e.g., when the metal traces are flush with the surrounding resin), the power may be disconnected, and the device may be removed for rinsing and drying.

The operations shown and described herein are provided to illustrate exemplary implementations for electroplating embossed features on a substrate. It is noted that the operations are not limited to the ordering shown. Still other operations may also be implemented.

It is noted that the exemplary embodiments shown and described are provided for purposes of illustration and are not intended to be limiting. Still other embodiments are also contemplated for electroplating embossed features on a substrate. 

1. A method for electroplating embossed features on a substrate, comprising: positioning a device in close proximity to an anode, the device having embossed trenches; delivering pressurized electrolyte to the anode; and activating electrical power between the anode and the device, wherein metal ions migrate into the embossed trenches to form electroplated metal traces on the device.
 2. The method of claim 1, further comprising fully wetting the anode before activating electrical power.
 3. The method of claim 1, further comprising applying pressure to the device to reduce space between the device and the anode.
 4. The method of claim 1, further comprising returning electrolyte to a reservoir.
 5. The method of claim 1, further comprising preventing short-circuiting even if the electroplated metal traces inadvertently contact the anode.
 6. The method of claim 1, further comprising forcing air between the anode and the electrolyte through pores formed in the anode.
 7. The method of claim 1, further comprising supplying the metal ions from the electrolyte.
 8. The method of claim 1, further comprising supplying the metal ions from the anode.
 9. A system for electroplating embossed features on a substrate, comprising: an anode configured to be positioned in close proximity to a device; a pump operating to deliver a pressurized electrolyte to the anode; and electrical power for connecting between the anode and the device, the electrical power causing metal ions to migrate onto exposed metal surfaces on the device to form electroplated metal traces.
 10. The system of claim 9, further comprising a planar production configuration.
 11. The system of claim 9, further comprising a roll-to-roll production configuration.
 12. The system of claim 9, wherein the device serves as a cathode for an electroplating circuit.
 13. The system of claim 9, wherein the anode is fully wetted before activating electrical power.
 14. The system of claim 9, wherein the anode is hydrophilic.
 15. The system of claim 9, wherein an outer layer of the anode is non-conductive ceramic to prevent short-circuiting even if the electroplated metal traces inadvertently contact the anode.
 16. The system of claim 9, wherein the anode is non-sacrificial and metal ions are provided at least in part from the electrolyte.
 17. The system of claim 9, wherein the anode is sacrificial and metal ions are provided at least in part from the anode.
 18. The system of claim 9, further comprising embossed trenches on the device, the embossed trenches corresponding to desired traces on the device to the electrolyte.
 19. A system for electroplating embossed features on a substrate, comprising: fluid delivery means for providing a metered flow of pressurized electrolyte to a device having embossed trenches; positive charge means for delivering metal ions into the embossed trenches of the device; and negative charge means for attracting the metal ions into the embossed trenches, wherein the metal ions migrate uniformly into the embossed trenches to form electroplated metal traces on the device.
 20. The method of claim 1, further comprising secondary means for providing metal ions.
 21. A system for electroplating embossed features on a substrate, comprising: a drum anode rotatably positioned directly adjacent to a device having resin-embossed features, the device in constant contact with substantially a same position on the drum anode while the drum rotates; a pump operating to deliver a continuous pressurized electrolyte inside the drum anode; pores formed in the drum anode to expel electrolyte onto the device as the device rotates over an external surface of the drum, and electrical power for connecting between the drum anode and the device, the electrical power causing metal ions to migrate through the pores onto exposed metal surfaces formed by the resin-embossed features on the device to form electroplated metal traces. 